1. Field of the Invention
The present invention relates to a gene implicated in abiotic stress tolerance and growth promotion and a method for improving abiotic stress tolerance and promoting growing of transformed plants with the same.
2. Description of the Related Art
Due to their sessile nature, higher plants are constantly faced with various adverse environmental factors, including drought, high salt, heavy metals, cold, heat shock, and ozone, during their whole life span. These abiotic stresses are a limiting factor for the growth and development of crop plants. Water deficiency causes dramatic reduction of crop production globally, and the decreasing availability of fresh water may pose a future threat to humans and higher plants. Plants have cellular and genetic defense mechanisms to enhance their tolerance to transient and long-term water shortages by triggering signaling network pathways and inducing stress-responsive genes (Shinozaki and Yamaguchi-Shinozaki, 2007). However, for stress tolerance or sensitivity, our knowledge concerning the biological functions of stress-related genes in higher plants is still rudimentary. Therefore, it is important to study the functions of stress responsive genes to increase the productivity of crop plants.
Plants have diverse defense strategies to reinforce their tolerance against unfavorable conditions by triggering signaling network pathways and inducing the stress-responsive genes. The present inventors have found that three AtSRP (Arabidopsis thaliana stress related protein) genes which encode homologs to the small rubber particle protein (SRPP) in rubber trees (Hevea brasiliensis) were rapidly induced by dehydration in Arabidopsis thaliana. Natural rubber is cis-1,4-polyisoprene produced through mevalonate pathway in cytosolic fractions (latex) of latex vessel tissues (Oh et al. 1999; Sookmark et al. 2002; Kim et al. 2004; Chow et al. 2007). Since Arabidopsis thaliana does not produce natural rubber, it was unexpected that the Arabidopsis thaliana water stress-induced genes shared sequence homology with rubber biosynthetic genes.
SRPP, originally known as a latex allergen, is a protein tightly bound on a small rubber particle in the latex of rubber trees (Hevea brasiliensis).
Bark tissue of rubber trees is constantly stripped, which is known as a tapping process, to collect rubber latex. Therefore, plugging of latex vessels is essential for rubber trees to prevent the loss of their cytoplasmic components, such as primary metabolites, and to prevent pathogen infection of the latex vessel tissues (Wititsuwannakul et al., 2008b). In the process of latex vessel plugging, hevein or Hevea latex lectin (HLL) interacts with rubber particle (RP) protein to form a rubber latex coagulum (Gidrol et al., 1994; Wititsuwannakul et al., 2008a). Recently, SRPP was purified as an RP glycoprotein that bound HLL and was, therefore, termed HLL-binding protein (HLLBP) (Wititsuwannakul et al., 2008c). Interaction between an N-acetylglucosamine moiety in SRPP and HLL may modulate the degree of latex coagulation in response to tapping and mechanical wounding.
However, roles of the SRPP associated with abiotic stresses such as drought, high salt and cold have been not known yet.
Throughout this application, various publications and patents are referred and citations are provided in parentheses. The disclosures of these publications and patents in their entities are hereby incorporated by references into this application in order to fully describe this invention and the state of the art to which this invention pertains.